SCL Flight Software

SCL Flight Software

Spacecraft Command Language (SCL) provides a scripting executive that allows priority-based parallel execution of scripts and rules for flight embedded systems. The SCL Real Time Engine (RTE) contains a rule-base Expert System and a command interpreter. The Expert System and command interpreter share the same code and behavior allowing the system to reduce the amount of code that must be verified and validated before flight.

The SCL system is designed to allow the same software architecture to be used for both flight and ground segments. Scripts developed and tested on the ground can be reused and moved directly onto the flight system with no loss of knowledge. The flight system allows closed loop control to be accomplished where ground contact is normally needed to make critical decisions. This paradigm shift reduces the need for ground personnel and lowers cost of ownership.

The SCL flight system can be integrated on top of a legacy system. The SCL flight software is designed to be reusable and has been fielded on many spacecraft missions, including:

• Clementine - Launched January 25, 1994

• FUSE - Launched June 24, 1999 - operated for 8 years

  • SCL also used in the ground station

• Interim Control Module (ICM) - Developed late 1990s (Not Flown)

  • Received Man-Rating from NASA

• EO-1/Autonomous Sciencecraft Experiment (ASE) - Operational on EO-1 since 2005

  • Co-Winner 2005 NASA Software Of The Year Award

• TacSat-2 - Launched December 16, 2006

• TacSat-3 - Launched May 19, 2009

• TacSat-4 - Launched September 27, 2011

• ORS Sat-1 - Launched June 29, 2011

SCL has been deployed in numerous simulators and testbed configurations in support of SCL and non-SCL spaceflight missions and other applications.

The SCL Flight software system includes:

• SCL Real Time Engine

  • Rule Based Expert System

  • Scheduling Manager

  • Command Execution Manager

• SCL shared memory database

• SCL decommutation engine

• SCL Packet Generator

• Software Message Bus - Compatible with the Real-Time Operating System

• SCL Compiler - workstation development environment

• Developer/User Interface - workstation development environment

For information on the SCL Ground Software click here.

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